JPH04303094A - Multistage sprocket device for bicycle - Google Patents

Abstract

PURPOSE:To perform chain rewrapping smoothly from a large diametral sprocket to a small diametral sprocket without making excessive flection force act on a chain by installing a link plate supporting part, supporting a link plate lower edge of the chain, in a side face of the small diametral sprocket side of a separation easy tooth of the large diametral sprocket. CONSTITUTION:Two adjacent teeth of a large diametral sprocket 4 are set down to each of separation easy teeth 9a, 9b, while a link plate receiving part 10 is formed in a side face of the small diametral sprocket side of these separation easy teeth 9a, 9b. This link plate receiving part 10 is made up of notching the side face of the small diametral sprocket side of a tip part 7 of the separation easy teeth 9a, 9b stepwise, through which a link plate of a chain C getting over the tip part 7 is received. In succession, two sprockets 2, 3 are set up so as to make length of a tangent hanging down from a chain connecting center 01 at a link plate rear end received by the link plate receiving part 10 to a center 02 of the small diametral sprocket 2 become np (p is a chain pitch and n is an integer).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-stage sprocket device for bicycles, and more particularly to a multi-stage sprocket device for bicycles, which is constructed so that a chain can be smoothly changed from a large-diameter sprocket to a small-diameter sprocket.

0002

[Prior Art] Modern bicycles have a chain wheel (front gear) attached to the crank and a freewheel (rear gear) attached to the rear hub, both of which have multiple sprockets with different numbers of teeth in parallel. Many gears are constructed with a multi-stage sprocket device and have an increased number of gears. A chain is connected between the front gear and the rear gear, and the rotational force input to the crank when the pedal is depressed is transmitted from the front gear to the rear gear via the chain, which causes the rear wheels to move. It is rotated to propel the bicycle forward. To shift gears, while the multi-stage sprocket device is rotating, the chain entering the multi-stage sprocket device is forcibly pushed in the direction of the hub axis by the derailleur, causing it to move diagonally.
This is done by disengaging it from the currently engaged sprocket and engaging it with the target sprocket. The quality of this shift is determined by how quickly the chain is disengaged from the currently engaged sprocket and how quickly the chain is brought into engagement with the target sprocket.

By the way, conventionally, regarding the performance of changing the chain from a large diameter sprocket to a small diameter sprocket,
By strongly pressing the chain entering the sprocket, the chain can be removed from any tooth position around the large-diameter sprocket, and the disengaged chain will automatically shift to the small-diameter sprocket due to tension. It was thought that For this reason, little consideration has been given to improving the performance of changing the chain from a large-diameter sprocket to a small-diameter sprocket.

However, since the number of teeth of the large-diameter sprocket and the small-diameter sprocket are different, when the chain is transferred from the large-diameter sprocket to the small-diameter sprocket, the chain of the small-diameter sprocket is at the position where it is about to engage, corresponding to this chain. The teeth of the small diameter sprocket mentioned above are not necessarily positioned. Therefore, even if the chain quickly separates from the large-diameter sprocket, it does not always mesh with the teeth of the small-diameter sprocket. In such a case, the chain roller will rotate for a while while riding on the tips of the teeth of the small diameter sprocket, that is, raised above the pitch circle of the sprocket, and the position of the roller in the circumferential direction of the sprocket and the position between the teeth of the sprocket will change. When these match, the chain meshes with the sprocket. That is, in the chain, after idling around the outer periphery of the small-diameter sprocket for a predetermined distance, the rollers fit between the teeth of the sprocket and engage with each other.

If the above phenomenon occurs in the rear gear (freewheel) when pedal force is applied, the roller rides on the tooth tip of the small diameter sprocket and spins idly, and the driving force is not transmitted to the chain and the drive is interrupted. Efficiency decreases. Moreover, after the chain has idly rotated to a position where the rollers of the chain engage with the teeth of the sprocket, the chain suddenly engages with the sprocket, and at this time, the driving force is also rapidly transmitted, giving a large shock to the rider. For this reason, not only the chain and sprocket may be damaged, but it may also pose a danger to the rider.

In order to solve the above problem, some of the teeth provided around the large-diameter sprocket are made easy-to-separate teeth, and the chain is removed from the large-diameter sprocket at the position where the easy-to-separate teeth are formed. A structure has been proposed in which the chain disengages quickly and adjusts the circumferential positions of the large diameter sprocket and the small diameter sprocket so that the chain disengaged from the large diameter sprocket is quickly and accurately engaged with the small diameter sprocket. For example, in 1987-
As described in Japanese Patent No. 40791, the distance between the center of one tooth of a large-diameter sprocket and the center of a tooth of a small-diameter sprocket on a tangential line in the direction of chain transfer from the large-diameter sprocket to the small-diameter sprocket is np- α (however, p
is the chain pitch, n is an integer, and α is a dimension smaller than the tooth height of the large-diameter sprocket. The teeth adjacent to the front in the rotational direction of the center are easy-to-leave teeth that allow the chain to detach toward the small-diameter sprocket more easily than other teeth.

[0007]

[Problems to be Solved by the Invention] However, when the chain meshing with the large diameter sprocket is pushed toward the small diameter sprocket during rotation of the multi-stage sprocket device and moved obliquely, the above-mentioned easy-to-separate teeth provided on the large diameter sprocket The inner link plate of the chain rides over the above-mentioned easy-to-separate teeth, and the inner link plate of the chain has a smaller diameter than the part meshing with the teeth in front of the above-mentioned easy-to-separate teeth. It will be forced to bend towards the sprocket side. As a result, the roller at the position immediately before the chain disengages cannot fit into the predetermined position between the teeth of the large-diameter sprocket, and the roller is lifted slightly outward in the radial direction of the sprocket compared to the normal meshing state. Become.

[0008] Then, as the sprocket continues to rotate from this state, the chain separated from the large diameter sprocket,
The chain tension pushes the sprocket radially inward. At this time, the chain is largely deflected toward the small-diameter sprocket in the hub axis direction due to interference with the teeth of the sprocket following the easy-to-separate tooth in the rotational direction, starting from the vicinity of the easy-to-separate tooth. The amount of this deflection increases as the link plate that has passed over the easy-to-separate teeth is pushed down radially inward, causing the chain moving from the large-diameter sprocket to jump over the outer teeth of the adjacent small-diameter sprocket without being able to catch them. Problems are likely to occur. In other words, the angle at which the chain moves obliquely becomes too large, making it difficult to mesh well with the outer teeth of the small-diameter sprocket.

For this reason, this does not pose much of a problem when applied to a front gear (chain wheel) where the gap between the large diameter sprocket and the small diameter sprocket is wide, but when applied to a rear gear (freewheel) where the gap between the large diameter sprocket and the small diameter sprocket is narrow. ), the problem arises that the bending of the chain in the direction of the small-diameter sprocket becomes too large as described above, making it impossible to accurately replace the chain with the small-diameter sprocket.

The present invention was devised under the above-mentioned circumstances, and solves the above-mentioned conventional problems, and not only allows the chain to be quickly and accurately separated from the large-diameter sprocket, but also quickly and accurately separates the chain from the small-diameter sprocket. To provide a multi-stage sprocket device configured to be able to mesh with a sprocket and to smoothly change a chain from a large-diameter sprocket to a small-diameter sprocket without applying an unreasonable bending force to the chain. That is the issue.

[0011]

[Means for Solving the Problems] In order to solve the above problems, the present invention takes the following technical measures. That is, the present invention provides a multi-stage sprocket device for a bicycle that includes at least one large-diameter sprocket and at least one small-diameter sprocket, in which at least two adjacent teeth of the large-diameter sprocket are arranged so that the chain has a smaller diameter than the other teeth. In addition to providing easy-to-separate teeth that easily separate in the direction of the sprocket, the lower edge of the link plate of the chain is supported on the small-diameter sprocket-side side surface of these easy-to-separate teeth at a position lower than the height of the teeth of the sprocket and higher than the tooth bottom. While providing a link plate support part, from the chain connection center of the rear end of the link plate supported by the link plate support part located rearmost in the rotational direction to the center between teeth of one of the small diameter sprockets rearward in the rotational direction. The length of the tangent line drawn down is np or np-α (however, p
is a chain pitch, n is an integer, and α is a value smaller than half of the length between adjacent teeth on the sprocket). shall be.

0012

Effects and Effects of the Invention In the present invention, at least two adjacent teeth of the large-diameter sprocket are easy-to-separate teeth. When the chain is pressed toward the small diameter sprocket, the chain will separate from the above-mentioned easy-to-separate teeth. At this time, the chain is lifted radially outward of the sprocket so as to ride on the tip of the easy-to-leave tooth at the forefront in the rotational direction, and rides over the easy-to-leave tooth.

Conventionally, the chain that has climbed over the easy-to-separate teeth is pushed down greatly from that part inward in the radial direction of the sprocket, and interferes with the side surface of the large-diameter sprocket on the small-diameter sprocket side, causing the chain to displace the part before it gets over the above-mentioned easily-separable teeth. On the other hand, the sprocket was largely deflected toward the small diameter sprocket. For this reason, the bending of the chain toward the small-diameter sprocket in the hub axial direction becomes larger than necessary, resulting in cases in which the chain cannot mesh well with the teeth of the small-diameter sprocket.

In the present invention, the chain that has climbed over the easy-to-separate teeth of the large-diameter sprocket has its lower edge connected to the link plate holder provided on the small-diameter sprocket side of the easy-to-separate tooth located rearward in the direction of rotation of the sprocket. Once supported by the branch, it is pushed down in the radial direction of the sprocket. The link plate support portion is configured to support the lower edge of the link plate at a position lower than the tooth height and higher than the tooth bottom. The easy-to-separate tooth according to the present invention is formed by deviating the tooth tip toward the large diameter sprocket so that the chain that is about to be replaced with the small diameter sprocket can easily get over the tooth tip. be done.

With the above configuration, in the multi-stage sprocket device according to the present invention, the chain detached from the large diameter sprocket is not immediately pushed down inward in the radial direction, but the lower edge of the link plate in the portion continuing rearward in the rotational direction. is once supported at a position higher than the bottom of the tooth in the link plate receiving portion of the easy-to-separate tooth, and then moved toward the small diameter sprocket. Therefore, the chain does not interfere with the rear tooth in the rotational direction and is not significantly bent in the hub axis direction. As a result, it is possible to maintain the chain's deflection appropriately, and there is no longer a risk that the chain may deflect too much after leaving the large-diameter sprocket and jump over the teeth of the adjacent small-diameter sprocket. It disappears. Therefore, it is possible to apply the present invention not only to a front gear where the gap between the large diameter sprocket and the small diameter sprocket is wide, but also to a rear gear where the gap between the large diameter sprocket and the small diameter sprocket is narrow.

Further, in the present invention, from the chain connection center of the rear end of the link plate supported by the link plate support portion located at the rearmost position in the rotational direction, to the gap between the teeth of one of the small diameter sprockets rearward in the rotational direction. The length of the tangent line drawn to the center is np or np-α (however,
The relative positions of the large-diameter sprocket and small-diameter sprocket in the circumferential direction are set so that p is the chain pitch, n is an integer, and α is a value smaller than half the length between adjacent teeth on the sprocket. .

[0017] A portion of the chain that is rearward of the portion supported by the link plate moves approximately linearly toward the outer periphery of the small diameter sprocket. Therefore, by setting the distance between the connection center of the rearmost chain supported by the link plate support part and the contact point of the tangent line lowered to the small diameter sprocket to np, the chain transitions from the large diameter sprocket to the small diameter sprocket. When it reaches the outer periphery of the small diameter sprocket, it can immediately mesh with the small diameter sprocket. This eliminates the possibility of the chain slipping around the outer periphery of the small-diameter sprocket and spinning idly, greatly improving shifting performance. Furthermore, when applied to the rear gear, the driving force generated by the front gear can be transmitted to the rear gear without loss, and the sudden transmission of the driving force can be avoided.

[0018] In addition, the distance between the chain connection center supported by the link plate support part and the center of the teeth of the small diameter sprocket is not only an integral multiple np of the chain pitch, but also a value slightly smaller than an integral multiple. The effects of the present invention can also be exhibited in the case of np-α. That is, by setting the length of the tangent to the contact point of the small diameter sprocket to be shorter than the substantial length of the chain, the rollers of the chain can be meshed with the small diameter sprocket with sufficient margin. Moreover, in reality, the large-diameter sprocket and the small-diameter sprocket are not on the same plane, but are placed at a certain interval, so the chain has to be moved diagonally at a predetermined angle with respect to the two sprockets. This is because it is necessary to adjust the length of the tangent line to be shorter than the actual length of the chain.

On the other hand, in the present invention, the value of α is set to a value smaller than half of the length between the teeth. This means that when the greatest common divisor of the number of teeth of the large diameter sprocket and the small diameter sprocket is a value of 2 or more, the same tangential length n is obtained at multiple positions at each interval dividing the circumference by the greatest common divisor.
This is to cope with the fact that if the greatest common divisor is 1, only one position where the interval is exactly np can be set.

In this case, it is possible to set approximate combinations for each interval obtained by dividing the outer periphery of the sprocket by the difference in the number of teeth between the large diameter sprocket and the small diameter sprocket.
The easy-to-separate teeth according to the present invention can be provided in this portion. In other words, even if the tangent length in one combination is np, the tangent length in other combinations will not be np,
Although it will be shifted by α, α in the above combination part
The value of should not exceed half the length between adjacent teeth. Therefore, the chain can be replaced smoothly in these parts.

As described above, the present invention makes it possible to adequately handle not only the front gear where the spacing between each sprocket is relatively wide, but also the rear gear where the spacing between each sprocket is narrow, making it possible to replace the chain. can be done accurately and quickly. As a result, it becomes possible to dramatically improve shift performance and safety when changing chains. In addition, the chain does not undergo large deflection and there is less interference with the side surfaces of the sprocket, which improves the life of the chain and sprocket.

[0022] The above-mentioned link plate receiving portion can be formed by cutting out the side surface of the small-diameter sprocket side of the tooth in which it is to be provided in a step-like manner from the top to the middle tooth height position, or It can be removed and formed into a chamfered shape. Alternatively, the tooth may be formed by removing the top portion of the tooth and making the tooth height lower than other teeth.

Furthermore, on the side surface of the small-diameter sprocket at the rear of the easy-to-separate teeth of the large-diameter sprocket in the rotational direction,
Providing a recess to reduce interference with the chain when transitioning from a large-diameter sprocket to a small-diameter sprocket alleviates the interference between the chain and sprocket, reduces chain deflection, and allows for smoother chain changes. It becomes possible. Furthermore, by providing the link plate receiving portion, the amount of bending of the chain itself is reduced, so there is no need to set the notch amount of the recessed portion so large, and problems regarding the strength of the teeth do not occur.

[0024]

[Description of Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 7. In this embodiment, the present invention is applied to a multi-stage freewheel (rear gear) for a bicycle. Furthermore, although FIG. 1 is a side view of the multi-stage sprocket device 1, in order to facilitate understanding of the following explanation, only one small-diameter sprocket 2 and one large-diameter sprocket 3 adjacent thereto are shown as representatives. Illustrated. In an actual multi-stage freewheel, 5 to 8 sprockets of different diameters are arranged in parallel, but there are small-diameter sprockets as described below between two adjacent large and small sprockets in these multiple sprockets. 2 and large diameter sprocket 3 apply.

As shown in FIGS. 1 and 2, a large number of teeth T are formed at equal intervals on the outer periphery of each sprocket 2, 3 at a pitch corresponding to the pitch P of the chain C. The chain C has teeth T on the outer periphery of the sprockets 2 and 3 protruding into the space between the pair of outer link plates 4a and 4b or the space between the pair of inner link plates 5a and 5b, and The connecting part of the chain, that is, the roller R, is fitted into the interdental part 6 formed between the teeth and the sprockets 2 and 3. The bottom of the interdental portion 6 forms an arcuate tooth bottom portion 8 having a slightly larger curvature than the outer diameter of the roller R.

In this embodiment, as shown in FIG.
Two adjacent teeth at three locations on the large-diameter sprocket 4 are used as easy-to-separate teeth 9a, 9b, and a link plate receiving portion 10 is formed on the side surface of each of the easy-to-separate teeth 9a, 9b on the small-diameter sprocket side. .

The easily removable teeth 9a, 9b according to this embodiment are as follows:
As shown in FIG. 2, by deviating the tooth tip 7 to the side opposite to the small diameter sprocket, the chain that is about to transition to the small diameter sprocket can easily overcome the tooth tip 7 and leave. It is formed. On the other hand, the link plate receiving portion 10 has the easily detachable teeth 9a, 9.
It is formed by cutting out the side surface of the small diameter sprocket side of the tooth tip 7 in a stepped manner, and the link plate of the chain C that has climbed over the tooth tip 7 is supported by this link plate support part 10. . In addition, as shown in FIG. 7, the teeth other than the easy-to-separate teeth 9a and 9b are arranged so that the chain C that is about to be transferred to the small-diameter sprocket 2 is moved by shifting the tooth tips 7 toward the small-diameter sprocket in the hub axis direction.
It has a difficult-to-separate shape that prevents it from being easily removed.

During the rotation of the multistage sprocket device 1, when the chain C meshing with the large diameter sprocket 3 is pushed in the direction of the small diameter sprocket 2 by a chain guide or the like, the chain C is moved toward the small diameter sprocket 2,
Overcome this at the above-mentioned easy-to-separate teeth 9a and 9b. Then, 1 which got over the tooth tips 7 of these easily separated teeth
A link plate is supported by the link plate support portion 10.

By the way, the chain C has a pair of outer link plates 4a, 4b and a pair of inner link plates 5a, 5b.
The gap between the outer link plates 4a, 4b and the gap between the inner link plates 5a, 5b are different in size. Therefore, due to the size of the gap, the link plate gets over the tips of the easy-to-separate teeth 9a and 9b, and
The manner in which the link plate is supported by the link plate support portion 10 is somewhat different.

That is, as shown in FIGS. 1 and 2,
When the outer link plates 4a, 4b of the chain C are located at the rearmost tooth 9b in the sprocket rotational direction among the easily detachable teeth 9a, 9b, the tooth 9b where the outer link plates 4a, 4b are located. The large-diameter sprocket-side inner link plate 5b of the chain C gets over the teeth 9a that are further forward in the rotational direction. The inner link plates 5a, 5b are forcibly bent toward the small-diameter sprocket in the hub axial direction with respect to the portion that meshes with the tooth 9n located one rotationally forward of the tooth 9a that the inner link plates 5a and 5b ride over. As a result, as shown in FIG. 1, the roller R cannot fit into the predetermined interdental position, and is held in a state where it is lifted outward in the radial direction of the sprocket compared to the normal meshing state. The amount of lift of this link plate is the largest, even when the large diameter sprocket 3
does not exceed the height of the teeth. As the sprocket continues to rotate from this state, the chain C tends to fall inward in the radial direction of the sprocket device 1 while further increasing its deflection in the hub axis direction due to tension.

In this embodiment, the above-mentioned easy-to-separate tooth 9a
The large diameter sprocket side inner link plate 5b that has overcome
is supported by a link plate support portion 10 provided at the tip of the easily removable tooth 9a. This link plate support part 10 is set at a position lower than the height of the tooth and higher than the bottom of the tooth, and the lower edge of the link plate 5b is held at this position. Therefore, the outer link plates 4a and 4b of the next chain C also enter the rearmost easy-to-leave tooth 9b while riding over the tooth tips 7 of the large-diameter sprocket 3. These outer link plates 4a, 4b are connected to inner link plates 5a, 5b located forward in the rotational direction of the sprocket.
However, as mentioned above, the gap between the plates of the outer link plates 4a, 4b is larger than that of the inner link plates 5a, 5b. The sprocket-side outer link plate 4b is also stably supported on the small-diameter sprocket-side side surface of the easily-separated tooth 9b by the link plate support portion 10 provided on the easily-separated tooth 9b. Furthermore, an inner link plate 5 following the outer link plates 4a and 4b supported by the rearmost link plate support portion 10
a, 5b begin to move downwardly tangent to the outer periphery of the small diameter sprocket 2 without engaging the tooth following the rearmost easy-to-separate tooth 9b.

On the other hand, as shown in FIG. 3, among the plurality of easily detachable teeth 9a, 9b, the inner link plates 5a, 5b of the chain C are attached to the rearmost tooth 9b in the direction of rotation of the sprocket.
is located, the easy-to-leave tooth 9b located at the rearmost position
The outer link plates 4a and 4b of the chain C corresponding to the tooth 9a in front of the chain C have a wide gap between the link plates, so even if this tooth 9a is formed to be easily detached, it is impossible to overcome this gap. . Therefore, the following large-diameter sprocket-side inner link plate 5b rides over the tooth tip 7 of the easy-to-separate tooth 9b located at the rearmost position in the sprocket rotational direction. Then, the large-diameter sprocket side inner link plate 5b that has passed over the tooth tip 7 of the easy-to-separate tooth 9b is supported by the link plate support portion 10 formed on the easy-to-separate tooth 9b, and the next outer link plate 5b The link plates 4a, 4b begin to move so that their tangent lines are directed down to the outer periphery of the small-diameter sprocket 2.

As described above, in the present invention, in any of the above cases, the rearmost easy-to-separate tooth 9b
The link plate corresponding to the large-diameter sprocket side tries to be pushed down inward in the radial direction of the large-diameter sprocket 3 by the tension of the chain C, but the link plate 4 on the large-diameter sprocket side
b and 5b are supported by the link plate support portion 10, so that the chain C can be moved in the direction of the small diameter sprocket without being suddenly and largely deflected.

Moreover, as shown in FIGS. 1 and 2, in this embodiment, on the side surface of the large-diameter sprocket 3 on the small-diameter sprocket side, there is a groove that moves from the chain connection center at the rear end of the link plate toward the small-diameter sprocket 2. Chain C
Since the recessed portion 11 is formed to prevent interference with the chain C, the chain C tends to fall inward in the radial direction of the large diameter sprocket 3.
The interference between the chain C and the side surface of the large-diameter sprocket 3 is alleviated, and the deflection of the chain C can be further suppressed.

Further, in this embodiment, as shown in FIG. 1, from the chain connection center O1 of the rear end of the link plate supported by the link plate support portion 10 formed on the rearmost tooth 9b in the rotational direction, , the length of the tangent L drawn to the center O2 of one tooth of the small-diameter sprocket 2 at the rear in the rotational direction is np, or np-α (where p is the chain pitch, n is an integer, and α is the adjacent tooth on the sprocket). The relative positions of the large-diameter sprocket 3 and the small-diameter sprocket 2 in the circumferential direction are set so that the distance between the large-diameter sprocket 3 and the small-diameter sprocket 2 is smaller than half of the length between the teeth.

By setting the length of the tangent line to np,
At the point of contact of the tangent L on the small diameter sprocket 2, the center O3 of the roller R of the chain C can be made to coincide with the inter-tooth center O2 of the small diameter sprocket 2. Therefore, when the chain C moving from the large-diameter sprocket 3 to the small-diameter sprocket 2 reaches the outer periphery of the small-diameter sprocket 2, the roller R fits perfectly between the teeth of the small-diameter sprocket 2 and engages with it.

Furthermore, as shown in FIG. 1, the distance to the interdental center O2 with which the tangent line L touches is not only set to an integral multiple np of the chain pitch, but also set to a value np-α that is slightly smaller than the integral multiple np. It is also applicable to cases where This is done by setting the length of the tangent line L up to the contact point of the small diameter sprocket 2 shorter than the actual length of the chain C, so that the roller R can be meshed with a margin between the teeth of the small diameter sprocket 2. Can be done. Moreover,
In reality, the large-diameter sprocket 3 and the small-diameter sprocket 2 are not on the same plane but are arranged at a constant interval, so the chain C is moved diagonally at a predetermined angle with respect to both the sprockets 2 and 3. This is because the length of the tangent line L needs to be adjusted to be shorter than the actual length of the chain C.

Further, in this embodiment, α is set to a value smaller than half of the length between the teeth. This means that when the greatest common divisor of the number of teeth of the large-diameter sprocket 3 and the small-diameter sprocket 2 is a value of 2 or more, the same tangent length np is placed at each interval obtained by dividing the circumference by the greatest common divisor. However, if the greatest common divisor is 1, it is possible to set only one tooth combination in which the above-mentioned interval is exactly np. .

In this case, combinations having similar tangential lengths can be set for each interval obtained by dividing the outer periphery of the sprocket by the difference in the number of teeth between the large diameter sprocket 3 and the small diameter sprocket 2. That is, even if the tangent length in one combination is np, the tangent length in other combinations will not be np, but will be shifted by α. However, the value of α in the above combination does not exceed half the length between adjacent teeth. Therefore, it becomes possible to smoothly replace the chain C at these combination parts. Therefore, even if the greatest common divisor of the large-diameter sprocket 3 and the small-diameter sprocket 2 is only 1, the easy-to-separate teeth 9 according to this embodiment are provided at multiple locations on the outer periphery of the large-diameter sprocket.
A, 9b can be provided and similar effects can be expected.

With the above configuration, in this embodiment, the chain C that has climbed over the easy-to-leave teeth 9a of the large-diameter sprocket 3 has the lower edges of its link plates 4b, 5b located at the rear in the rotational direction of the sprocket. It is supported by a link plate receiving portion 10 provided on the tooth 9b, and the portion following it is pushed down inward in the radial direction of the sprocket. That is, in this embodiment, the chain C detached from the large-diameter sprocket 3 is not immediately pushed down in the radial direction, but is once supported by the link plate support portion 10 and then pushed toward the small-diameter sprocket 2. Replaced. Therefore, the chain C immediately after detaching from the large-diameter sprocket 3 is not significantly bent in the hub axis direction. As a result, it is possible to appropriately maintain the chain flexure during the replacement stroke, and unlike conventional methods, the chain flexure immediately after detaching from the large diameter sprocket 3 becomes too large, causing the teeth of the adjacent small diameter sprocket to become too large. There is no longer any problem of jumping over something.

In addition, in this embodiment, from the chain connection center O1 of the rear end of the link plate supported by the link plate support part 10 to the inter-tooth center O2 of one of the small diameter sprockets 2 rearward in the rotational direction. Since the length of the lowered tangent L is set to np or np-α, the chain C moving from the large-diameter sprocket 3 to the small-diameter sprocket 2 reaches the outer circumference of the small-diameter sprocket 2 and at the same time, the small-diameter sprocket 2 can be meshed with. This eliminates the possibility that the chain C slips on the outer periphery of the small diameter sprocket 2 and spins idly, and the shifting performance is significantly improved. Moreover, in this embodiment, a recess is formed on the side surface of the small-diameter sprocket at the rear of the easy-to-separate teeth 9a, 9b of the large-diameter sprocket 3 in the rotational direction to alleviate the interference of the chain C transitioning from the large-diameter sprocket 3 to the small-diameter sprocket 2. Since the entrance portion 11 is provided, the bending of the chain C is further alleviated, and the shifting performance is further improved.

With the above configuration of this embodiment, when changing the chain C from the large diameter sprocket 3 to the small diameter sprocket 2, the chain C transferred from the large diameter sprocket 3 is
It is possible to always mesh the small diameter sprocket 2 accurately and quickly, and therefore the chain C can be stably replaced from the large diameter sprocket 3 to the small diameter sprocket 2, which was unstable in the past. Moreover, driving safety can also be improved. Furthermore, during gear shifting, the chain C is not greatly bent and no excessive force is applied to the sprocket, so the life of the chain and sprocket is improved.

As a result, the multi-stage sprocket device 1 according to this embodiment can be applied not only to a front gear (chain wheel) where the spacing between each sprocket is relatively wide, but also to a rear gear (freewheel) where the spacing between each sprocket is narrow. It is also possible to apply this method to other vehicles, making it possible to significantly improve gear shifting performance.

The scope of the present invention is not limited to the above-described embodiments. The embodiment is an example in which the present invention is applied to a multi-stage freewheel (rear gear), but it can be similarly applied to a multi-stage chain wheel (front gear) formed by arranging a plurality of sprockets of different diameters in parallel. . Further, in the embodiment, two adjacent teeth are formed as easily releasable teeth, but three or more teeth may be formed as easily releasable teeth. In addition, in the embodiment, a substantially step-shaped link plate support part was provided, but as shown in FIG. A link plate receiving portion can also be formed by removing the link plate. Alternatively, it may be formed by removing the top of the tooth where it should be provided and making the tooth height lower than other teeth. Further, the position where the link plate support portion is provided is not limited to the example, and may be any position that is lower than the height of the tooth and higher than the bottom of the tooth.

[Brief explanation of the drawing]

FIG. 1 is a side view of a multi-stage sprocket device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation of the multi-stage sprocket device in FIG. 1, and is a view taken in the direction of arrow II in FIG.

FIG. 3 is a diagram illustrating the operation of the multi-stage sprocket device in FIG. 1;
It is a figure corresponding to the II direction arrow view of FIG.

FIG. 4 is a sectional view taken along line IV-IV in FIG. 2;

FIG. 5 is a diagram showing another embodiment, and is a diagram corresponding to FIG. 4.

6 is a sectional view taken along the line VI-VI in FIG. 2. FIG.

7 is a sectional view taken along the line VII-VII in FIG. 2. FIG.

[Explanation of symbols]

1 Multi-stage sprocket device 2 Small diameter sprocket 3 Large diameter sprocket 4a, 4b, 5a, 5b Link plate 9a, 9b
Easy-to-separate tooth 10 Link plate support portion 11 Recessed portion O1 Chain connection center O2 Interdental center

Claims (5)

[Claims] Claim 1: A multi-stage sprocket device for a bicycle comprising at least one large-diameter sprocket and at least one small-diameter sprocket, in which at least two adjacent teeth of the large-diameter sprocket are arranged so that the chain has a smaller diameter than the other teeth. In addition to providing easy-to-separate teeth that easily separate in the direction of the sprocket, the lower edge of the link plate of the chain is supported on the small-diameter sprocket-side side surface of these easy-to-separate teeth at a position lower than the height of the teeth of the sprocket and higher than the tooth bottom. While providing a link plate support part, from the chain connection center of the rear end of the link plate supported by the link plate support part located rearmost in the rotational direction to the center between teeth of one of the small diameter sprockets rearward in the rotational direction. The length of the lowered tangent is np or np-α (where p is the chain pitch, n is an integer, and α is a value smaller than half the length between adjacent teeth on the sprocket). A multi-stage sprocket device for a bicycle, characterized in that the relative positions of the large diameter sprocket and the small diameter sprocket in the circumferential direction are set. 2. The link plate receiving portion is formed by cutting out the small-diameter sprocket-side side surface of the tooth on which it is to be provided in a substantially step-like manner from the top thereof to an intermediate position of the tooth height. The multi-stage sprocket device for a bicycle according to claim 1. 3. The link plate receiving portion is formed by chamfering the small-diameter sprocket-side side surface of the tooth on which it is to be provided from the top to the intermediate tooth height position. 1. The multi-stage sprocket device for a bicycle according to 1. 4. The multi-stage sprocket device for a bicycle according to claim 1, wherein the link plate support portion is formed by removing the top of the tooth on which it is to be provided and making the tooth height lower than other teeth. . 5. A recessed portion is provided on the side surface of the small-diameter sprocket at the rear of the easy-to-separate tooth of the large-diameter sprocket in the direction of rotation to reduce interference with the chain transitioning from the large-diameter sprocket to the small-diameter sprocket. A multistage sprocket device for a bicycle according to any one of claims 1 to 4.